1. Field of the Invention
The present invention relates to a scanning-start-point detecting method, a scanner, and an image information reading method and an image information reader employing the scanning-start-point detecting method.
2. Description of the Related Art
With the rapid development of techniques in the genetic engineering field in recent years, an enzyme-immunity measuring method, a fluorescent antibody method and the like taking advantage of an antigen-antibody reaction have been utilized in diagnoses and research. Techniques of searching for deoxyribonucleic acid (DNA) having influence on various genetic diseases have also advanced. As one of the methods, attention has been paid to a micro array technique.
The micro array technique is a technique which employs a micro array chip (also called a DNA chip), such as that shown in FIG. 4, previously coated with a great number of interpreted cDNA fragments (an example of specific bound matters) differing from one another at high density (intervals of less than a few 100 .mu.m) in matrix form at predetermined intervals as dots on a membrane filter, or a slide glass. For instance, DNA fragments (an example of organism-originated matters) are taken out from the cell of healthy subject A and labeled with fluorochrome a, while DNA fragments are taken out from the cell of subject B having a genetic disease and labeled with fluorochrome b. The labeled DNA fragments are dropped on the micro array chip by means of a pipette or the like, whereby the DNA fragments of each subject and the CDNA fragments on the micro array chip are hybridized. Then, each cDNA fragment on the micro array chip is repeatedly scanned by light beams which excite the fluorochromes a and b, respectively. Next, fluorescence emitted from each CDNA fragment is detected by photoelectric read means such as a photomultiplier tube (PMT), a charge-coupled device (CCD) and the like. Based on the results of detection corresponding to the positions of the emitted fluorescence on the micro array chip, it is judged which of the CDNA fragments has been hybridized by the DNA fragment of each subject. By comparing the cDNA fragments hybridized between both subjects, the DNA fragment manifested or lost by the above-mentioned disease is specified.
In the relative, repetitive scanning between the above-mentioned exciting light and micro array chip, incidentally, there is a need to detect a position at which reading starts (a reading start point) in order to obtain the start timing of the collection of read data. The reading start point forms part of the scanning line that exciting light passes through. Therefore, an optical sensor or the like is provided in a portion having a fixed positional relation with the disposed position of the micro array chip. It is common practice for the position, obtained after the scanning time or clock count corresponding to the above-mentioned positional relation has elapsed or counted since the passage of exciting light was detected by the optical sensor, to be detected as a reading start point.
Also, the aforementioned reading-start-point detecting method is not limited to reading the above-mentioned micro array chip but is performed similarly in the case where the relative, horizontal scanning between a reading medium and a head which reads out recorded information from the reading medium is repeatedly performed in a fixed direction so that the information is read out from the reading medium, or in the case where the relative, horizontal scanning between a recording medium and a head which records information on the recording medium is repeatedly performed in a fixed direction so that the information is recorded on the recording medium.
However, the reading-start-point detecting method and the recording-start-point detecting method (both referred to generically as a scanning-start-point detecting method) have to provide a detector, such as an optical sensor for detecting a scanning start point, separately from the horizontal scanning means, as describe above. Furthermore, there is a need to ensure space for installing this detector in the horizontal scanning line, which means that the detector will be a hindrance to achieving device miniaturization. In addition, in scanners, which deal with various kinds of reading media or recording media (both referred to generically as media to be scanned) differing in length in the scanning direction, there is a need to attach detectors at positions corresponding to these media to be scanned, respectively, and consequently, there is a problem that (1) the number of hardware components increases, (2) the cost rises accordingly, and (3) it takes time to design and manufacture the device.
Moreover, the above-mentioned relative, repetitive scanning between exciting light and a micro array chip is performed by a combination of horizontal scanning which is repeatedly moved within a fixed range in the going and returning directions and vertical scanning in a direction perpendicular to the horizontal scanning direction, but reading is performed by emitting exciting light only in the going direction of the horizontal scanning.
The chief reason for this is that, in the read operation in the returning direction, the reading start point varies with the length in the scanning direction of a sample to be scanned and therefore it is difficult from the standpoint of costs and installation space to provide start-point detectors at different positions and that there is a problem that a pixel difference will arise between the image information read out in the going direction and the image information read out in the returning direction.
As described above, the reading-start-point detecting method is not limited to reading the micro array chip but is performed similarly in the case where the relative, horizontal scanning between a reading medium and a head which reads out recorded information from the reading medium is repeatedly performed in a fixed direction so that the information is read out from the reading medium, or in the case where the relative, horizontal scanning between a recording medium and a head which records information on the recording medium is repeatedly performed in a fixed direction so that the information is recorded on the recording medium.
However, in order to read out the above-mentioned medium to be scanned, such as a sample, at a higher speed or record information on the medium at a higher speed, it is effective to perform reading or recording in the returning direction as well as in the going direction.